Cross-linkable coating composition and method of producing the same

ABSTRACT

The instant invention provides cross-linkable coating compositions, process for producing the same, and substrates coated therewith. The cross-linkable coating composition comprises: (a) polyaldehyde, or acetal or hemiacetal thereof; (b) an acid catalyst having pKa of less than 6; (c) a liquid media; (d) an acrylic polycarbamate comprising at least an average of 2.0 carbamate functional groups, wherein said polycarbamate has a glass transition (Tg) of less than 25° C.; and (e) one or more fillers having a pH in the range of equal to or less than 9 and/or one or more pigments having a pH in the range of equal to or less than 9, and/or one or more additives having a pH in the range of equal to or less than 9, wherein said composition has a curing temperature in the range of less than 70° C.

FIELD OF INVENTION

The instant invention relates to cross-linkable coating compositions,process for producing the same, and substrates coated therewith.

BACKGROUND OF THE INVENTION

The use of polymeric materials, e.g. polyurethane based paints derivedfrom isocyanates, in coating applications is generally known. However,polyurethane based paints derived from isocyanates have environmentaland health concerns due to the use of isocyanates in the preparation ofsuch coating compositions. Furthermore, commercially availableisocyanate-free polyurethane paints do not cure under ambienttemperatures, i.e. a temperature in the range of from 0° C. to 60° C.Additionally, wind turbine blade coating compositions are required toprovide protection against collision with particulates such as raindrops. The wind blade industry also desires coating formulations withlonger pot life and faster dry time to improve the coating process ofthe large wind blades.

Therefore, there is a need for a coating composition capable of beingcured at ambient conditions while providing necessary flexibility anddurability required for protecting wind turbine blades without theenvironmental and health concerns of conventional polyurethane coatingsderived from isocyanates.

SUMMARY OF THE INVENTION

The instant invention provides cross-linkable coating compositions,process for producing the same, and substrates coated therewith.

In one embodiment, the instant invention provides a cross-linkablecoating composition comprising: (a) polyaldehyde, or acetal orhemiacetal thereof; (b) an acid catalyst having pKa of less than 6; (c)a liquid media; (d) an acrylic polycarbamate comprising at least anaverage of 2.0 carbamate functional groups, wherein said polycarbamatehas a glass transition (Tg) of less than 25° C.; and (e) one or morefillers having a pH in the range of equal to or less than 9 and/or oneor more pigments having a pH in the range of equal to or less than 9,and/or one or more additives having a pH in the range of equal to orless than 9, wherein said composition has a curing temperature in therange of less than 70° C.

In an alternative embodiment, the instant invention further provides aprocess for producing a cross-linkable coating composition comprisingthe steps of: (a) selecting a polyaldehyde, or acetal or hemiacetalthereof; (b) selecting an acid catalyst having pKa of less than 6; (c)selecting a liquid media; (d) selecting a acrylic polycarbamatecomprising at least an average of 2.0 carbamate functional groupswherein said polycarbamate has a glass transition (Tg) of less than 25°C.; (e) selecting one or more fillers having a pH in the range of equalto or less than 9, and/or one or more pigments having a pH in the rangeof equal to or less than 9, and/or one or more additives having a pH inthe range of equal to or less than 9; (f) contacting said polyaldehyde,or acetal or hemiacetal thereof; said acid catalyst; said liquid media,said polycarbamate, said one or more filler, and optionally said one ormore pigments; and (g) thereby forming a crosslinkable coatingcomposition; wherein said composition has a curing temperature in therange of less than 70° C.

In another alternative embodiment, the instant invention furtherprovides a coated substrate comprising a substrate; and one or more filmlayers derived from the inventive cross-linkable coating compositionassociated with at least one surface of said substrate.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the coated article is the rotor blade.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the rotor blade is a wind turbine blade, ahelicopter blade, or an aircraft blade.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the substrate comprises one or more metals, oneor more plastics, one or more composite materials, and one or more filmsderived from one or more primers.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the polycarbamate has a glass transition (Tg)of less than 0° C.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the one or more film layers have a thickness inthe range of from 5 to 500 μm.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the one or more films have an MEK resistance inthe range of from greater than 50 double rubs.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the one or more films have rain erosionresistance of greater than 30 minutes.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the polyaldehyde, acetal or hemiacetal thereofhas from 2 to 20 carbon atoms or from more than 20 carbon atoms, withthe proviso that a polyaldehyde having more than 20 carbon atoms has atleast one aldehyde group for every 10 carbon atoms.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the polyaldehyde, acetal or hemiacetal thereofis selected from the group consisting of(cis,trans)-1,4-cyclohexanedicarboxyaldehydes,(cis,trans)-1,3-cyclohexanedicarboxyaldehydes, and mixtures thereof.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the acrylic polycarbamate component hascarbamate groups and hydroxyl groups in a ratio of the equivalents ofcarbamate groups to the number of equivalents of hydroxyl functionalgroups of from 1:1 to 20:1.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the cross-linkable coating composition furthercomprises one or more curing inhibitors.

In an alternative embodiment, the instant invention provides across-linkable coating composition, process for producing the same,coated articles made therefrom, in accordance with any of the precedingembodiments, except that the curing inhibitor is chosen from water, analcohol or a mixture thereof.

DETAILED DESCRIPTION OF THE INVENTION

The instant invention provides cross-linkable coating composition,process for producing the same, and substrates coated therewith.

The cross-linkable coating composition according to the presentinvention comprises: (a) polyaldehyde, or acetal or hemiacetal thereof;(b) an acid catalyst having pKa of less than 6; (c) a liquid media; (d)an acrylic polycarbamate comprising at least an average of 2.0 carbamatefunctional groups, wherein said polycarbamate has a glass transition(Tg) of less than 25° C.; and (e) one or more fillers having a pH in therange of equal to or less than 9 and/or one or more pigments having a pHin the range of equal to or less than 9, and/or one or more additiveshaving a pH in the range of equal to or less than 9, wherein saidcomposition has a curing temperature in the range of less than 70° C.

Polyaldehyde Component, or Acetal or Hemiacetal Thereof

The cross-linkable coating composition comprises a polyaldehydecomponent, or acetal or hemiacetal thereof. In one embodiment, thepolyaldehyde component comprises from 2 to 20 carbon atoms. In anotheralternative embodiment, the polyaldehyde comprises greater than 20carbon atoms, with the proviso that a polyaldehyde having more than 20carbon atoms has at least one aldehyde group for every 10 carbon atoms.

The crosslinkable composition may comprise from 2 to 50 percent byweight of the polyaldehyde component or acetal or hemiacetal thereof;for example, from 5 to 25 percent by weight of the polyaldehydecomponent or acetal or hemiacetal thereof. In one embodiment, thepolyaldehyde is selected from the group consisting of(cis,trans)-1,4-cyclohexanedicarboxyaldehydes,(cis,trans)-1,3-cyclohexanedicarboxyaldehydes, pentane-1,5-dial,ethane-1,2-dial, and mixtures thereof.

For example, the polyaldehyde component can have two or more aldehydegroups. Suitable polyaldehydes of the present invention can have two,three, four or more aldehyde groups.

The polyaldehyde component can be a cyclic, straight or branched; cyclicand non-aromatic; or cyclic and aromatic.

The polyaldehyde component can comprise one or more cyclic, non-aromaticpolyaldehydes or one or more aromatic polyaldehydes. For example, thepolyaldehyde component can comprise one or more cyclic, non-aromaticpolyaldehydes having from 3 to 20 ring carbon atoms, and may consistessentially of one or more cyclic, non-aromatic polyaldehydes havingfrom 3 to 20 ring carbon atoms.

Each cyclic, non-aromatic polyaldehyde component can independently havefrom 5 to 12 ring carbon atoms, and, can be a mixture of(cis,trans)-1,4-cyclohexanedicarboxyaldehydes and(cis,trans)-1,3-cyclohexanedicarboxyaldehydes.

Examples of suitable cyclic polyaldehydes aretrans-1,3-cyclohexanedicarboxaldehyde;cis-1,3-cyclohexanedicarboxaldehyde;trans-1,4-cyclohexanedicarboxaldehyde;cis-1,4-cyclohexanedicarboxaldehyde; a mixture of1,3-cyclohexanedicarboxaldehydes and 1,4-cyclohexanedicarboxaldehydes,preferably a 1-to-1 mixture thereof;exo,exo-2,5-norbornanedicarboxaldehyde;exo,exo-2,6-norbornanedicarboxaldehyde;exo,endo-2,5-norbornanedicarboxaldehyde;exo,endo-2,6-norbornanedicarboxaldehyde;endo,endo-2,5-norbornanedicarboxaldehyde;endo,endo-2,6-norbornanedicarboxaldehyde product (endo and exo mixture);3-(3-formylcyclohexyl)propanal; 3-(4-formylcyclohexyl)propanal;2-(3-formylcyclohexyl)propanal; 2-(4-formylcyclohexyl)propanal; andcyclododecane-1,4,8-tricarbaldehyde and a mixture containing one or moreof 2,8-, 3,8-, and 4,8-di(formyl)tricyclo[5.2.1.0^(2,6)]decane.

The trans-1,3-cyclohexanedicarboxaldehyde;cis-1,3-cyclohexanedicarboxaldehyde;trans-1,4-cyclohexanedicarboxaldehyde; andcis-1,4-cyclohexanedicarboxaldehyde can be prepared by a processcomprising hydroformylating 3-cyclohexene-1-carboxaldehyde using thehydroformylating conditions described herein.

The 1:1 mixture of 1,3- and 1,4-cyclohexanedicarboxaldehydes can beprepared by a process comprising reacting acrolein and 1,3-butadiene ina Diels-Alder reaction to give 3-cyclohexenecarboxaldehyde (also called1,2,3,6-tetrahydrobenzaldehyde), and hydroformylating the3-cyclohexenecarboxaldehyde.

The exo,exo-2,5-norbornanedicarboxaldehyde;exo,exo-2,6-norbornanedicarboxaldehyde;exo,endo-2,5-norbornanedicarboxaldehyde;exo,endo-2,6-norbornanedicarboxaldehyde;endo,endo-2,5-norbornanedicarboxaldehyde; andendo,endo-2,6-norbornanedicarboxaldehyde product (endo and exo mixture)can be prepared by a process comprising reacting acrolein andcyclopentadiene in a Diels-Alder reaction to give a2-norbornene-5-carboxaldehyde, and hydroformylating the2-norbornene-5-carboxaldehyde.

The 3-(3-formylcyclohexyl)propanal; 3-(4-formylcyclohexyl)propanal;2-(3-formylcyclohexyl)propanal; and 2-(4-formylcyclohexyl)propanal canbe prepared by a process comprising hydroformylating vinyl cyclohexene.

The cyclododecane-1,4,8-tricarbaldehyde can be prepared by a processcomprising trimerizing 1,3-butadiene to give 1,4,8-cyclododecatriene,and hydroformylating the 1,4,8-cyclododecatriene.

The mixture of 2,8-, 3,8-, and4,8-di(formyl)tricyclo[5.2.1.0^(2,6)]decane can be prepared by a processcomprising hydroformylating dicyclopentadiene.

The polyaldehyde component can be unblocked and unprotected or blockedor protected. Blocked or protected polyaldehydes can be formed byreacting an unblocked and unprotected polyaldehyde with a suitableblocking or protecting group. Examples of protecting or blocking groupsfor aldehyde groups are bisulfites (e.g., from reaction of thepolyaldehyde with sodium bisulfite), dioxolanes (e.g., from reaction ofthe polyaldehyde with ethylene glycol), oximes (e.g., from reaction ofthe polyaldehyde with hydroxylamine), imines (e.g., from reaction of thepolyaldehyde with methylamine), and oxazolidines (e.g., from reaction ofthe polyaldehyde with a 2-aminoethanol).

Preferred aldehyde protecting groups are, and preferred protectedpolyaldehydes comprise, a hydrated group (>C(OH)₂), hemiacetal, acetal,or imine. These preferred protected polyaldehydes can be prepared byrespectively reacting the polyaldehyde with water; one mole equivalentof an alkanol (e.g., methanol or ethanol); two mole equivalents of thealkanol; or ammonia or a primary amine (e.g., methylamine). Thehemiacetal, acetal, or imine protecting group can, if desired, beremoved by a deprotection such as hydrolysis to give back theunprotected form of the polyaldehyde. Such aldehyde protecting orblocking groups and formation and removal (i.e., deprotection) istaught, for example, in U.S. Pat. No. 6,177,514 B1.

Preferably, the polyaldehyde is stable in neat form (i.e., does notmaterially self-polymerize) and, more preferably, is substantially waterinsoluble and is stable in neat form.

The polyaldehydes of the present invention can be prepared by anysuitable means, including oxidation of corresponding polyols, and viabatchwise and continuous processes for preparing the polyaldehydes.Preferably the polyaldehyde is prepared by hydroformylating asubstantially water-insoluble mono-olefin containing aldehyde compound,substantially water-insoluble multi-olefin containing aldehyde compound,or a substantially water-insoluble multi-olefin containing startingcompound (collectively referred to herein for convenience assubstantially water-insoluble olefin-containing compounds). Thehydroformylation step can be performed by any conventional means such aswith hydrogen gas, carbon monoxide, and the olefin-containing startingcompound. Preferably the hydroformylating step is performed in a manneras generally described in U.S. Pat. No. 6,252,121 B1, which describes animproved separation process.

Preparations of the polyaldehyde can optionally further comprisereversibly blocking or protecting aldehyde groups of the polyaldehydeswith aldehyde blocking or protecting groups to give a blocked orprotected polyaldehyde, respectively. The protected polyaldehyde can beemployed in place of or in addition to the polyaldehyde component.

Preferably, the polyaldehyde component can be a mixture comprising twoor more of trans-1,3-cyclohexanedicarboxaldehyde,cis-1,3-cyclohexanedicarboxaldehyde,trans-1,4-cyclohexanedicarboxaldehyde andcis-1,4-cyclohexanedicarboxaldehyde, or protected or blocked forms ofthese polyaldehydes.

Acid Catalyst Component

The cross-linking coating composition comprises 0.1 to 5 percent byweight of one or more acid catalysts; for example, from 0.5 to 3 weightpercent, or from 0.5 to 2 weight percent, based on the total weight ofthe crosslinkable coating composition.

The acid catalyst component may be any acid catalyst suitable forpromoting the reaction between the acrylic carbamate functionalcomponent and the polyaldehyde component. In one embodiment, the acidcatalyst may be a Lewis acid. In another embodiment, the acid catalystmay be a protic acid. In one embodiment, the acid catalyst has a pKa ofless than 6.0, or in the alternative, a pKa of less than 4.0.

The curing step of the present invention is initiated by an acidcatalyst. Such initiation can be performed by exposure to heat for aperiod of time sufficient to produce the inventive crosslinkedcomposition. The heat can be applied radiantly although other means suchas by convection or combinations of means can be used.

Any compound, substance or material suitable for increasing a rate ofreaction of a carbamate group with an aldehyde group (—C(═O)H) can beemployed as the acid catalyst. Examples of acid catalysts are Lewisacids (e.g., boron trifluoride etherate) and protic acids (i.e.,Brønsted acids). The acid catalyst can comprise a protic acidcharacterizable as having a pK_(a) of 6 or less, wherein pK_(a) isnegative base-10 logarithm of acid dissociation constant, K_(a), of theprotic acid.

A preferred protic acid is an inorganic protic acid or organic proticacid. A preferred inorganic protic acid is phosphoric acid or sulfuricacid. A preferred organic protic acid is carboxylic acid, phosphonicacid, or sulfonic acid. A preferred carboxylic acid is acetic acid,trifluoroacetic acid, propionic acid, or a dicarboxylic acid. Apreferred phosphonic acid is methylphosphonic acid. A preferred sulfonicacid is methanesulfonic acid, benzenesulfonic acid, a camphorsulfonicacid; para-toluenesulfonic acid, or dodecylbenzenesulfonic acid.Examples of suitable Lewis acid curing catalysts are AlCl₃;benzyltriethylammonium chloride (TEBAC); Cu(O₃SCF₃)₂; (CH₃)₂BrS⁺Br⁻;FeCl₃ (e.g., FeCl₃.6H₂O); HBF₄; BF₃.O(CH₂CH₃)₂; TiCl₄; SnCl₄; CrCl₂;NiCl₂; and Pd(OC(O)CH₃)₂.

The acid catalyst can be unsupported (no solid support) or supported,i.e. covalently bonded to a solid support. Examples of supported acidcatalysts are supported curing catalysts such as supported acidcatalysts such as acid (H⁺) forms of cation exchange-type polymer resins(e.g., ethanesulfonic acid,2-[1-[difluoro[(1,2,2-trifluoroethenyl)oxy]methyl]-1,2,2,2-tetrafluoroethoxy]-1,1,2,2-tetrafluoro-,polymer with 1,1,2,2-tetrafluoroethene, available under the trade nameNAFION NR 50 (E. I. du Pont de Nemours & Co., Inc., Wilmington, Del.)and ethenylbenzenesulfonic acid polymer with diethenylbenzene availableunder the trade name AMBERLYST™ 15 (Rohm and Haas Co., subsidiary of TheDow Chemical Company, Midland, Mich., USA).

Liquid Media Component

The cross-linkable coating composition can comprise from 0 to 90 percentby weight of one or more solvents; for example, from 20 to 70, or from30 to 50, percent by weight of one or more solvents. Solvents may beneeded for reducing the viscosity of the cross-linkable coatingcomposition to facilitate application to a substrate. Solvents may alsobe required to maintain all the components of the cross-linkable coatingcomposition in one single phase. Such solvents include, but are notlimited to, organic solvents. Exemplary solvents include, but are notlimited to, ethanol, ethylene glycol monoalkyl ethers, diethylene glycolmonoalkyl ethers, propylene glycol monoalkyl ethers and dipropyleneglycol monoalkyl ethers.

Alternative examples of suitable organic solvents are non-polar or polarorganic solvents such as, for example, an alkane (e.g., a(C₆-C₁₂)alkane), aromatic hydrocarbons (e.g. toluene, xylene) ether(e.g., (C₂-C₁₂)ether, e.g., a (C₂-C₁₂)dialkyl ether), carboxylic ester(e.g., a (C₂-C₁₂)carboxylic ester), ketone (e.g., a (C₃-C₁₂)ketone),secondary or tertiary carboxamide (e.g., a secondary or tertiary(C₃-C₁₂)carboxamide), sulfoxide (e.g., a (C₂-C₁₂)sulfoxide), or amixture of two or more thereof.

In one embodiment, water can be used as a solvent or additive, providedthat the amount of water does not result in a two-phase composition.

Acrylic Polycarbamate Component

The acrylic polycarbamate component comprises at least an average of 2.0carbamate functional groups, and has a glass transition of less than 25°C., for example from −50 to less than 5° C. Unless otherwise notedherein, the term “carbamate functional group” means a radical structureof formula

In one embodiment, the acrylic polycarbamate is prepared by reacting thehydroxyl groups of an acrylic polyol with an unsubstituted carbamic acidalkyl ester (such as methyl carbamate) or urea in the presence of acatalyst at elevated temperatures using a transesterification procedurethat is known by one skilled in the art. In one embodiment, at least 40%of the hydroxyl groups in the acrylic polyol are converted to carbamategroups, or in the alternative, at least 60%, or in another alternative,at least 80%. The acrylic polyols are well known in the art and can beprepared from polymerizing a hydroxyl-functional (meth)acrylate such as2-hydroxyethyl(meth)acrylate with other (meth)acrylic monomers, such asmethyl methacrylate, acrylic acid, butyl acrylate, and the like. Thepolymerization can be performed using a variety of processes (such assolution polymerization) that are known by one skilled in the art.

In another embodiment, the acrylic polycarbamate can also be prepared bypolymerizing a carbamoylalkyl(meth)acrylate with other (meth)acrylicmonomers, such as methyl methacrylate, acrylic acid, butyl acrylate, andthe like as well as other co-monomers such as styrene, acrylonitrile andthe like.

Such acrylic polycarbamates can have a molecular weight in the range offrom 1000 to 100,000, or in the alternative, in the range of from 1500to 10,000. As used herein, molecular weight refers to the number averagemolecular weight, which may be determined by gel permeationchromatography (GPC) using a polystyrene standard. The glass transitiontemperature of the acrylic polycarbamate preferably is less than 25° C.,for example from −50 to less than 5° C. The glass transition temperature(T_(g)) of the acrylic polycarbamate may be determined by a variety ofmethods such as differential scanning calorimetry (DSC). In oneembodiment, the carbamate functionality of the acrylic polycarbamate canbe at least 2, or in the alternative, at least 3, or in the alternative,at least 4.

In one embodiment, the acrylic polycarbamate component can be producedvia batch process or continuous process. In one embodiment, one or moreacrylic polycarbamates, which are optionally dissolved in a solvent,e.g. organic solvent, or in the alternative, melted via heat.

In one embodiment, the acrylic polycarbamate has carbamate groups andhydroxyl groups in a ratio of the equivalents of carbamate groups to thenumber of equivalents of hydroxyl functional groups of from 1:1 to 20:1.

Other Components

In one embodiment, the cross-linkable coating composition can compriseone or more curing inhibitor agents. Exemplary curing inhibitor agentsinclude, but are not limited, to alcohols and/or water and/or mixturesthereof. Exemplary curing inhibitor agents include, but are not limitedto primary alcohols such as ethanol, n-propanol, and n-butanol.

The cross-linkable coating composition may comprise from 0 to 50 percentby weight of the one or more curing inhibitor agents; for example, from2 to 30, or from 10 to 20, percent by weight of the curing inhibitoragents.

In one embodiment, the cross-linkable coating composition can compriseone or more pigments having a pH in the range of equal to or less than9. Exemplary pigments include, but are not limited to, TiO₂, lamp black,and talc.

In one embodiment, the cross-linkable coating composition can compriseone or more fillers having a pH in the range of equal to or less than 9.Exemplary fillers include, but are not limited to, clay, barium sulfate,and silica.

In one embodiment, the cross-linkable coating composition can compriseone or more additives having a pH in the range of equal to or less than9. Exemplary additives include, but are not limited to, ultraviolet (UV)light stabilizers, dispersing agents, flow & leveling agents andrheology agents. Such additional additives will, of course, depend onthe intended use of the coating composition. Typically usefulconventional formulation additives include UV light stabilizers(hindered amines) such asBis-(1-octyloxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate (Tinuvin 123supplied by BASF) and2,4-bis[N-Butyl-N-(1-cyclohexyloxy-2,2,6,6-tetramethylpiperidin-4-yl)amino]-6-(2-hydroxyethylamine)-1,3,5-triazine(Tinuvin 152 supplied by BASF); pigment and filler dispersing additivessuch as polyphosphoric acid polyesters (Disperbyk 110 supplied by BYKUSA, Inc); and flow and leveling agents such as polyether modifiedpolydimethylsiloxanes (BYK 333 supplied by BYK USA, Inc); and rheologymodifiers such as organowaxes (Troythix XYZ supplied by TroyCorporation).

Process for Producing the Cross-Linkable Coating Composition

The process for producing a cross-linkable coating composition accordingto the present invention comprises the steps of: (a) selecting apolyaldehyde, or acetal or hemiacetal thereof; (b) selecting an acidcatalyst having pKa of less than 6; (c) selecting a liquid media; (d)selecting a acrylic polycarbamate comprising at least an average of 2.0carbamate functional groups wherein said polycarbamate has a glasstransition (Tg) of less than 25° C.; (e) selecting one or more fillershaving a pH in the range of equal to or less than 9, and/or one or morepigments having a pH in the range of equal to or less than 9, and/or oneor more additives having a pH in the range of equal to or less than 9;(f) contacting said polyaldehyde, or acetal or hemiacetal thereof; saidacid catalyst; said liquid media, said polycarbamate, said one or morefiller, and optionally said one or more pigments; and (g) therebyforming a crosslinkable coating composition; wherein said compositionhas a curing temperature in the range of less than 70° C.

The inventive crosslinkable composition can be made in batch process viaany conventional mixing device under ambient temperature and pressure.

The cross-linked coating compositions of the present invention, eventhose produced by curing at room temperature, have a high degree ofcrosslinking.

Coated Substrates

The coated substrates of the present invention comprise a coating layerderived from the inventive cross-linkable coating composition, which isin contact to at least a portion of a substrate capable of being coated.

The inventive coated substrates can be prepared by any suitable method.For example, in a method of coating a surface of a substrate, the methodcomprises applying the inventive cross-linkable coating composition toat least a portion of a surface of a substrate and curing at a curingtemperature of 70° C. or less, or, for example, 30° C. or less, so as toprepare a coated substrate comprising a crosslinked composition.

The inventive crosslinkable coating composition can be applied to thesurface of the substrate(s) by any suitable applying means such as, forexample, brushing, calendaring, rolling, spraying, mopping, troweling,or dipping. The substrate being coated can be of any shape including,for example, a flat or rolled sheet (e.g., cylinder), sphere, beads,finely divided particles, and the like. The surface of the substratebeing coated can be irregular or regular, continuous or discontinuous,porous or non-porous, jointed or not jointed.

The substrates suitable for being coated independently can comprise anymaterial. Examples of suitable material are wood, metal, ceramic,plastic, composite materials, and/or glass.

The coated article comprises a coated substrate comprising a layer ofthe inventive cross-linked coating composition in contact with at leasta portion of a substrate.

The inventive coating exhibits pendulum hardness (7 day) in the rangegreater than 20, for example 20 to 200.

The coatings of the present invention exhibit resistance to organicsolvent, i.e., methyl ethyl ketone (MEK) back-and-forth double rubbing(i.e., one rub back, one rub forth equals one double rub) of 50 orgreater, or in the alternative, 70 or greater, or in the alternative 100or greater, or in the alternative from 50 to 200.

The inventive coating exhibits a cross-hatch adhesion value of from 1 Bto 5 B, for example, from 2 B to 5 B, or in the alternative from 3 B to5 B, or in the alternative from 4 B to 5 B, or in another alternative 5B.

In determining any one or more of the aforementioned pendulum hardness,cross-hatch adhesion value, and number of MEK double rubs(back-and-forth), the coating is formed on a steel substrate asdescribed herein. The inventive coating had a thickness, as measured asdescribed later, of from 10 micrometers (μm) to 250 μm, more preferably50 μm or more.

The curing of the cross-linkable coating composition can be completedwithin 7 days or less, for example, within 5 days or less, or within 24hours or less, or within 12 hours or less.

Examples

The following examples illustrate the present invention but are notintended to limit the scope of the invention. The examples of theinstant invention demonstrate capability of being cured at ambientconditions while providing necessary flexibility and durability requiredfor protecting wind turbine blades without the environmental and healthconcerns of conventional polyurethane coatings derived from isocyanates

Formulation Components

Ti-Pure® R-900—titanium dioxide supplied by DuPont (pigment)Ti-Pure® TS6200—titanium dioxide supplied by DuPont (pigment)Optiwhite®—calcined aluminum silicate supplied by Burgess Pigment(filler)Acematt® TS 100—silica supplied by Evonik Industries (filler)Cimbar™UF-—barium sulfate supplied by Cimbar Performance Minerals(filler)n-Butyl acetate supplied by Dow Chemical (organic solvent)Aromatic 150 supplied by ExxonMobil (organic solvent)Ethanol supplied by Fisher Scientific (organic solvent)Cycat® 4040—40% solution of p-toluenesulfonic acid in isopropanolsupplied by Cytec (acid catalyst)

Acrylic Polyol Components

HEMA—hydroxyethyl methacrylate (Rocryl 400 (HEMA-LA)) supplied by TheDow Chemical Companyn-BA—n-Butyl acrylate supplied by the The Dow Chemical Company2-EHA—2-ethylhexyl acrylate supplied by The Dow Chemical CompanyMMA—methyl methacrylate supplied by The Dow Chemical CompanyIBoMA—Isobornyl methyacrylate supplied by SartomerGlacial Acrylic Acid—supplied by The Dow Chemical Companyt-BPAc—t-butyl peroxyacetate (Luperox 7M50) supplied by ArkemaXylenes—supplied by Fisher ScientificAmyl Acetate—supplied by Fisher ScientificIso-butanol—supplied by Fisher ScientificAcrylic Polyol A is an acrylic polyol with a solution OH EW of 592,solids content of 86.4% in amyl acetate, xylene, and iso-butanol, andhas a T_(g) of −21.9° C. and greater than 2 hydroxyl functional group.Acrylic Polyol A is prepared according to the following process andbased on the formulation components reported in Table 1_(i).

Process for Preparing Acrylic Polyol A

A 5 L, 3-neck round bottom flask equipped with an adapter allowing 2feed lines to enter the reactor. The middle neck of the flask isequipped with a nitrogen line inlet and a Teflon stir bearing and mixingshaft. The third neck has a Claison adapter with a thermocouple and aFreidrich's condenser.

The monomers are charged to a glass jar and placed on a balance. Theinitiator and solvent are charged to a jar and placed on a balance. Themonomer and initiator are added to the flask using 2 FMI pumps. The flowrate for the monomer blend is 3.35 g/min. The initiator blend flow rateis 0.74 g/min.

Initial charge of 117 g of solvent blend is added to the flask andheated to 140° C. using a heating mantle, with gentle stirring and lownitrogen flow. When the flask reaches 140° C., the monomer and initiatorpumps are started. The flow rate is monitored by weight loss. When themonomer and initiator jars are empty, ˜5 g of solvent blend is added tothe jar and added to the flask through the pumps to rinse the transferlines. Then the chaser initiator (3.34 g in 15.4 g solvent blend) ispumped through the initiator pump at the same flow rate and then flushedwith ˜5 g of the solvent blend.

Solvent Blend: 55% amyl acetate/42% xylenes/3% iso-butanolInitiator: 50% t-BPAc in mineral spiritsAcrylic polyol B is an acrylic polyol with a solution OH EW of 521,solids content of 76.4% in xylene and iso-butanol, and has a T_(g) of−24.9° C. and greater than 2 hydroxyl functional group.Acrylic Polyol B is prepared according to the following process andbased on the formulation components reported in Table 1_(i).

Process for Preparing Acrylic Polyol B

A 5 L, 3-neck round bottom flask equipped with an adapter allowing 2feed lines to enter the reactor. The middle neck of the flask isequipped with a nitrogen line inlet and a Teflon stir bearing and mixingshaft. The third neck has a Claison adapter with a thermocouple and aFreidrich's condenser.

The monomers are charged to a glass jar and placed on a balance. Theinitiator and solvent are charged to a jar and placed on a balance. Themonomer and initiator are added to the flask using 2 FMI pumps. The flowrate for the monomer blend is ˜10 g/min. The initiator blend flow rateis ˜2.2 g/min.

Initial charge of 350 g of solvent blend is added to the flask andheated to 140° C. using a heating mantle, with gentle stirring and lownitrogen flow. When the flask reaches 140° C., the monomer and initiatorpumps are started. The flow rate is monitored by weight loss. When themonomer and initiator jars are empty, ˜15 g of solvent blend is added tothe jar and added to the flask through the pumps to rinse the transferlines. Then the chaser initiator is pumped through the initiator pump atthe same flow rate and then flushed with ˜15 g of the solvent blend.

Solvent Blend: 93% xylenes/7% iso-butanolInitiator: 50% tBPAc in mineral spiritsAcrylic Polyol C is an acrylic polyol with a solution OH equivalentweight (EW) of 572, solid content of 74.3% in xylene, and has a T_(g)−14° C. Acrylic Polyol C is prepared according to the following processand based on the formulation components reported in Table 1_(i).

Process for Preparing Acrylic Polyol C

A 5 L, 2 piece round bottom reactor equipped with 5 port head is used.The middle neck of the head is equipped with a Teflon stir bearing andmixing shaft. One side neck has an adapter allowing 2 feed lines toenter the reactor, another neck has a thermocouple, another neck has anitrogen inlet and the last neck is equipped with a Freidrich'scondenser.

The monomers are charged to a glass jar and placed on a balance (3000 gbatch). The initiator and solvent are charged to a jar and placed on abalance. The monomer and initiator are added to the reactor using 2 FMIpumps. The flow rate for the monomer blend is 19.0 g/min. The initiatorblend flow rate is 2.76 g/min which is calculated to feed the initiatorfor 15 minutes longer than the monomers to act as a chaser.

Initial charge of 345 g of solvent added to the flask and heated to 140°C. using a heating mantle, with gentle stirring and low nitrogen flow.When the flask reaches 140° C. the nitrogen flow is stopped and 5% ofthe monomer mix is added as a heel, once back at reflux 5% of theinitiator blend is added and the monomer and initiator pumps arestarted. The flow rate is monitored by weight loss. The contents areheld at temperature for 15 additional minutes after the initiator feedis depleted. At this time 194 g of solvent is added and allowed to mixfor 15 additional minutes before being poured out.

Solvent: Xylenes

Initiator: 50% t-BPAc in mineral spiritsAcrylic Polyol D is an acrylic polyol with a solution OH EW of 579.6,solids content of 76.2% in xylene, and has a T_(g) 12.5° C. AcrylicPolyol D is prepared according to the following process and based on theformulation components reported in Table 1_(i).

Process for Preparing Acrylic Polyol D

A 5 L, 2 piece round bottom reactor equipped with 5 port head is used.The middle neck of the head is equipped with a Teflon stir bearing andmixing shaft. One side neck has an adapter allowing 2 feed lines toenter the reactor, another neck has a thermocouple, another neck has anitrogen inlet and the last neck is equipped with a Freidrich'scondenser.

The monomers are charged to a glass jar and placed on a balance (3000 gbatch). The initiator and solvent are charged to a jar and placed on abalance. The monomer and initiator are added to the reactor using 2 FMIpumps. The flow rate for the monomer blend is 20.0 g/min. The initiatorblend flow rate is 2.91 g/min which is calculated to feed the initiatorfor 15 minutes longer than the monomers to act as a chaser.

Initial charge of 345 g of solvent added to the flask and heated to 140°C. using a heating mantle, with gentle stirring and low nitrogen flow.When the flask reaches 140° C. the nitrogen flow is stopped and themonomer and initiator pumps are started. The flow rate is monitored byweight loss. The contents are held at temperature for 15 additionalminutes after the initiator feed is depleted. At this time 194 g ofsolvent is added and allowed to mix for 15 additional minutes beforebeing poured out.

Solvent: Xylenes

Initiator: 50% t-BPAc in mineral spiritsAcrylic Polyol E is an acrylic polyol with a solution OH EW of 611.8,solids content of 77.3% in xylene, and has a T_(g) −24.3° C. AcrylicPolyol E is prepared according to the following process and based on theformulation components reported in Table 1_(i).

Process for Preparing Acrylic Polyol E

A 5 L, 3-neck round bottom flask equipped with an adapter allowing 2feed lines to enter the reactor. The middle neck of the flask isequipped with a nitrogen line inlet and a Teflon stir bearing and mixingshaft. The third neck has a Claison adapter with a thermocouple and aFreidrich's condenser.

The monomers are charged to a glass jar and placed on a balance (3000 gbatch). The initiator and solvent are charged to a jar and placed on abalance. The monomer and initiator are added to the reactor using 2 FMIpumps. The flow rate for the monomer blend is 20.0 g/min. The initiatorblend flow rate is 2.91 g/min which is calculated to feed the initiatorfor 15 minutes longer than the monomers to act as a chaser.

Initial charge of 345 g of solvent added to the flask and heated to 140°C. using a heating mantle, with gentle stirring and low nitrogen flow.When the flask reaches 140° C. the nitrogen flow is stopped and themonomer and initiator pumps are started. The flow rate is monitored byweight loss. The contents are held at temperature for 15 additionalminutes after the initiator feed is depleted. At this time 194 g ofsolvent is added and allowed to mix for 15 additional minutes beforebeing poured out.

Solvent: Xylenes

Initiator: 50% t-BPAc in mineral spirits

TABLE 1_(i) HEMA BA 2-EHA MMA IBoMA AA Weight Weight Weight WeightWeight Weight t-BPAc Polyol % % % % % % % A 30 70 — — — — 4 B 30 — 56 14— — 4 C 30 — 49 20 — 1 4 D 30 — 40 14.5 14.5 1 4 E 30 — 69 — — 1 4

Acrylic Carbamate Polymers

Comparative Polycarbamate 1 is prepared using acrylic polyol ParaloidAU-608X, which is commercially available from The Dow Chemical Company.Paraloid AU-608X has a solution OH equivalent weight (EW) of 1120,solids content of 58% in xylene, and has a T_(g) 46° C. Comparative 1has greater than 2 functional group. Additional properties are measuredand listed in Table 1.

Acrylic Polyol (Paraloid AU-608X) was charged to a 500 ml 3-neck roundbottom flask equipped with a mechanical stirrer, Dean-Stark trap,condenser, and nitrogen bubbler system. 54.05 g of methyl carbamate wasadded along with 1.06 g of dibutyltin oxide (carbamylation catalyst) tothe 3-neck reaction flask. The flask was purged with nitrogen and heatedto 140° C. As the temperature was increased, methanol was collected inthe Dean-Stark trap and the volume recorded. The reaction was allowed tocontinue until the methyl carbamate was consumed as determined by C13NMR—disappearance of the methyl resonance from the methyl carbamate(52.2 ppm) using Mercury Vx 400 MHz NMR from Agilent Technologies.Characterization of the polycarbamate included percent solids (weightloss), OH number (titration), and DSC for T_(g). Additional propertiesare measured and listed in Table 1. The approximate carbamate conversionwas 86%.

Inventive Polycarbamate A is prepared using an acrylic polyol (AcrylicPolyol A) with a solution OH EW of 592, solids content of 86.4% in amylacetate, xylene, and iso-butanol, and has a T_(g) of −21.9° C. andgreater than 2 carbamate functional group.

Acrylic Polyol A was charged to a 500 ml 3-neck round bottom flaskequipped with a mechanical stirrer, Dean-Stark trap, condenser, andnitrogen bubbler system. 54.05 g of methyl carbamate was added alongwith 1.06 g of dibutyltin oxide (carbamylation catalyst) to the 3-neckreaction flask. The flask was purged with nitrogen and heated to 140° C.As the temperature was increase, methanol was collected in theDean-Stark trap and the volume recorded. The reaction was allowed tocontinue until the methyl carbamate was consumed as determined by C13NMR—disappearance of the methyl resonance from the methyl carbamate(52.2 ppm) using Mercury Vx 400 MHz NMR from Agilent Technologies. Theapproximate carbamate conversion was 74%. Characterization of thepolycarbamate included percent solids (weight loss), OH number(titration), and DSC for T_(g). Additional properties are measured andlisted in Table 1.

Inventive Polycarbamate B is prepared using an acrylic polyol (AcrylicPolyol B) with a solution OH EW of 521, solids content of 76.4% inxylene and iso-butanol, and has a T_(g) of −24.9° C. and greater than 2carbamate functional group.

Acrylic Polyol B was charged to a 500 ml 3-neck round bottom flaskequipped with a mechanical stirrer, Dean-Stark trap, condenser, andnitrogen bubbler system. 54.05 g of methyl carbamate was added alongwith 1.06 g of dibutyltin oxide (carbamylation catalyst) to the 3-neckreaction flask. The flask was purged with nitrogen and heated to 140° C.As the temperature was increased, methanol was collected in theDean-Stark trap and the volume recorded. The reaction was allowed tocontinue until the methyl carbamate was consumed as determined by C13NMR—disappearance of the methyl resonance from the methyl carbamate(52.2 ppm) using Mercury Vx 400 MHz NMR from Agilent Technologies.Characterization of the polycarbamate included percent solids (weightloss), OH number (titration), and DSC for T_(g). Additional propertiesare measured and listed in Table 1. The approximate carbamate conversionwas 96%.

Inventive Polycarbamate C is prepared using acrylic polyol (AcrylicPolyol C) with a solution OH equivalent weight (EW) of 572, solidcontent of 74.3% in xylene, and has a T_(g) −14° C. Additionalproperties are measured and listed in Table 1. The approximate carbamateconversion was 84%.

Inventive Polycarbamate D is prepared using an acrylic polyol (AcrylicPolyol D) with a solution OH EW of 579.6, solids content of 76.2% inxylene, and has a T_(g) 12.5° C. Additional properties are measured andlisted in Table 1. The approximate carbamate conversion was 79%.

Inventive Polycarbamate E is prepared using an acrylic polyol (AcrylicPolyol E) with a solution OH EW of 611.8, solids content of 77.3% inxylene, and has a T_(g) −24.3° C. Additional properties are measured andlisted in Table 1. The approximate carbamate conversion was 67%.

CHDA 1—1,3/1,4-Cyclohexanedicarboxaldehyde, 88% solids with a EW of 78.8(polyaldehyde)CHDA 2—1,3/1,4-Cyclohexanedicarboxaldehyde, 82.72% solids with a EW of84.6 (polyaldehyde).

TABLE 1 Carba- CEW mate CEW¹ (Solu- Solids T_(g) Mn Function- (Solid)tion) (Wt. %) (° C.) (daltons) ality² Polycarbamate 1 800 1294 61.8 36.33572 4.5 Polycarbamate A 730 1278 57.1 −17.7 6042 8.3 Polycarbamate B458 581 78.8 −13.9 4325 9.4 Polycarbamate C 552 728 75.8 4.0 5000 9.0Polycarbamate D 602 828 72.7 22.6 3400 5.6 Polycarbamate E 748 987 75.8−6.0 4600 6.1 ¹CEW = Carbamate Equivalent Weight ²CarbamateFunctionality = Mn/CEWThe carbamate equivalent weight (CEW) on solids is calculated using thefollowing equation: CEW=[OH EW_(polyol)+(43×CarbamateConversion)]÷Carbamate Conversion, where the carbamate conversion isapproximated using the following equation:

Carbamate Conversion=(OH #_(polyol)−OH #_(polycarbamate))÷OH #_(polyol)

Inventive Coating Examples 1-3 (IE-1-3) and Comparative Coating ExampleA (CE-A)

The Inventive Coating Examples 1-3 (IE-1-3) and Comparative CoatingExample A (CE-A) containing pigments and fillers were prepared in aFlackTek SpeedMixer™ (Model DAC 600 FV-K, FlackTek, Inc.) dualasymmetric centrifuge. The formulations were prepared based on thefollowing process based on the formulation components listed in Table 2.

1. The polycarbamate polymer, Ti-Pure R900 and Optiwhite or Cimbar UFwere added to a max 300 SpeedMixer cup. The polymer and fillers weremixed by hand with a spatula to pre-wet the fillers.2. The formulation was mixed for approximately 1 min at 2300 rpm andvisually checked and then the contents on the side of the cup were mixedin by hand with a spatula.3. Step 2 was repeated.4. Approximately half of the silica was added to the cup and mixed byhand with a spatula to pre-wet the silica.5. The formulation was mixed for approximately 1 min at 2300 rpm andvisually checked and then the contents on the side of the cup were mixedin by hand with a spatula.6. Step 5 was repeated.7. The remaining silica was added to the cup and mixed by hand with aspatula to pre-wet the silica.8. The formulation was mixed for approximately 1 min at 2300 rpm andvisually checked and then the contents on the side of the cup were mixedin by hand with a spatula.9. Step 8 was repeated.10. The Aromatic 150 was added to the cup and mixed by hand with aspatula.11. The formulation was mixed for approximately 1 min at 2300 rpm andvisually checked and then the contents on the side of the cup were mixedin by hand with a spatula.12. The n-butyl acetate was added to the cup and mixed by hand with aspatula.13. The formulation was mixed for approximately 1 min at 2300 rpm andvisually checked and then the contents on the side of the cup were mixedin by hand with a spatula.14. The ethanol and Cycat 4040 were added to the cup and mixed by handwith a spatula.15. The formulation was mixed for approximately 1 min at 2300 rpm andvisually checked and then the contents on the side of the cup were mixedin by hand with a spatula.16. Just prior to coating application the CHDA (polyaldehydecrosslinker) was added to the cup and mixed for approximately 1 min.

Coating Substrate

The composite airfoil substrates are shown in FIG. 1. The coatingsapplied to the substrate had an average thickness of 0.010 to 0.015inches, and a maximum thickness limited to 0.040 inches. Each specimenhad a maximum weight of 200 g.

Inventive Coated Substrates 1-2 (ICS-1 and ICS-2) and Comparative CoatedSubstrate A (CCS-A)

The primer, as described below and Table 2, was spray applied tocomposite airfoil substrates to a nominal dry film thickness of ˜100 μmand allowed to cure for 24 hours at ambient conditions. The primedcomposite airfoil substrates were then sanded with 120 grit sandpaperprior to applying the top coat. The top coat formulations were allowedto cure for at least 7 days at 50% relative humidity and 22° C. Theproperties of ICS-1, ICS-2, and CCS-A were tested for their properties,and the results are reported in Table 3.

Inventive Coated Substrate 3 (ICS-3)

The composite airfoil substrate was sanded prior to coating. The topcoat formulations were spray applied to un-primed composite airfoilsubstrates.

The top coat formulations were allowed to cure for at least 7 days at50% relative humidity and 22° C. The properties of ICS-3 were tested fortheir properties, and the results are reported in Table 3.

Formulation Components for the Primer

DER 3680X90 is an epoxy resin solution supplied by The Dow ChemicalCompany.GNS SG-8008 is an epoxy reactive diluent supplied by GNS Technologies,LLC, a subsidiary of The Dow Chemical Company.BYK 104S is a pigment dispersing agent (solution of a lower molecularweight unsaturated polycarboxylic acid polymer and a polysiloxanecopolymer) supplied by BYK Additives & Instruments.BYK 501 is a defoaming agent (solution of foam destroying polymers,silicone free) supplied by BYK Additives & Instruments.Wollastocoat 10ES is a filler (wollastonite aka calcium orthosilicate)supplied by NYCO.Halox SZP-391 is a corrosion inhibitor (Strontium Zinc Phosphosilicate)supplied by Halox.Blanc Fixe is a filler (precipitated barium sulfate) supplied bySachtleben.Red Iron Oxide is a pigment supplied by Lanxess.Bentone SD-2 is a rheology modifier additive (an organic derivative of abentonite clay) supplied by Elementis.Xylenes is a solvent supplied by Fisher Scientific.Dowanol PMA is a solvent supplied by The Dow Chemical Company.Methyl isobutyl Ketone (MIBK) is a solvent supplied by FisherScientific.Ancamine K-54 is a epoxy hardener (2,4,6-Tri(dimethylaminomethyl)phenol) supplied by Air Products.GNS GS-140 is an epoxy hardener (polyamide) supplied by GNSTechnologies, LLC, a subsidiary of The Dow Chemical Company.

Primer Formulation and Preparation

Epoxy/Polyamide Primer Part A & Part B were prepared based on theformulation components and according to the process described in Table2.

TABLE 2 Material Name Wt Percent (Based on the PART A total weight ofPart A) Grind - Combine and mix with high speed disperser to a 5-6Hegman DER 3680X90 17.77 GNS SG-8008 2.64 Xylene 8.88 BYK 104S 0.38 BYK501 0.38 Wollastocoat 10 ES 25.98 Halox SZP-391 7.63 Blanc Fixe 14.44Red Iron Oxide 8.08 Bentone SD-2 1.35 Grind Sub-total 87.53 LetDown -Add DER 3680X90 to grind above while mixing, then add Dowanol PMA, MIBK,and Xylene - mix until homogenous DER 3680X90 8.55 Dowanol PMA 1.30 MIBK1.59 Xylene 1.03 Total 100 Wt Percent (based on PART B total weight of BPart) Premix - Combine GS-140, Ancamine and xylene in a paint can andmix until homogenous GNS GS-140 72.2 Ancamine K-54 Dan 9.4 Xylene 18.4Total 100.0

Prior to coating application, the Part A and Part B of theepoxy/polyamide primer formulation were combined at a ratio of 7.2:1 byweight and mixed until homogenous.

TABLE 3 Eq Wt CE-A IE-1 IE-2 IE-3 Solids (Solu- Weight Weight WeightWeight (wt %) tion) (g) (g) (g) (g) Polycarbamate 1 61.8 1294 148.4 — —— Polycarbamate A 57.1 1278 — 272 — 162.8 Polycarbamate B 78.8 581 — —137 Barytes UF 100 — 47.2 48.2 — 28.86 Optiwhite 100 — — — 14.7 —Ti-Pure R900 100 — 21.41 65.83 13.25 38.18 Acematt TS 100 100 — 10.2317.55 6.6 10.51 Aromatic 150 0 — 32.2 34.1 39 17.8 n-butyl acetate 0 —14 29.7 17 16.3 Ethanol 0 — 13.6 22.2 16.9 13.3 Cycat 4040 40 — 2 3.41.87 2.04 CHDA 1 88 78.8 — 16.8 — 10 CHDA 2 82.72 84.6 9.7 — 19.9 —

TABLE 4 Time (min) Example 15 30 45 60 CCS-A 5% 40-45% erosion erosionICS-1 No No Damage No Damage No Damage Damage ICS-2 No No Damage NoDamage No Damage Damage ICS-3 No No Damage No Damage Damage

Example CCS-A illustrates that a high T_(g) polymer does not yield acoating that can pass the rain erosion test.

Examples ICS-1 & ICS-2 illustrate that low T_(g) polymers are requiredto pass the rain erosion test. These examples also illustrate thatdifferent levels of pigment/fillers and types can be used in the topcoat formulation and pass the rain erosion test.

Example ICS-3 illustrates that a primer is not necessary for the topcoat to have excellent adhesion and pass the rain erosion test.

Inventive Coating Examples 4-6 (IE-4-6)

The Inventive Coating Examples 4-6 (IE-4-6), i.e. coating formulationscontaining pigments, were prepared in a FlackTek SpeedMixer™ (Model DAC150, FlackTek, Inc.) dual asymmetric centrifuge. The substrates andcoating formulations were prepared based on the following process andaccording to the formulation components listed in Table 5.

Substrate Preparation

Using commercially available paper towel, iron phosphate treated steelsubstrates (from Q-panel company, Type R-412-I, size: 4×12×0.032 inch)were cleaned with isopropanol thoroughly and then air-dried forapproximately between 5 to 10 minutes.

Coating Formulation Preparation

The polycarbamate component and pigment were charged into a speed mixercup, and mixed approximately 60-120 seconds at 3000 rpm or until mixedwell. Solvent (n-butyl acetate) was added and mixed another 60 secondsat 3000 rpm. The sides scraped and were mixed 60 seconds at 3000 rpmagain. Ethanol & acid catalyst (Cycat4040) were added, and mixed for 60seconds at 3000 rpm. The sides of the cup were scraped, and CHDA 2 wasadded and mixed for 30 seconds at 3000 rpm.

Inventive Coated Substrates 4-6 (ICS-4-6)

The coating formulations were applied to substrates using the 10 milscoating applicator (#24 8-path coating applicator from P.G.&T.CO.) toachieve 2-3 mils coating dry film thickness. The coating formulationswere cured in the humidity control room (50% RH, ˜24° C.) for 7 daysbefore testing; thereby forming ICS-4, ICS-5, and ICS-6. The propertiesof ICS-4, ICS-5, and ICS-6 were tested, and the results are reported inTable 6.

TABLE 5 IE-4 IE-5 IE-6 Solids Eq Wt Weight Weight Weight (w %)(Solution) (g) (g) (g) Polycarbamate C 75.8 728 52.24 — — PolycarbamateD 72.7 828 — 54.88 — Polycarbamate E 75.8 987 — 53.43 TS-6200 100 —14.85 14.96 15.19 n-butyl acetate 0 — 16.31 14.07 16.28 Ethanol 0 — 9.29.2 9.2 Cycat 4040 40 — 1.34 1.34 1.33 CHDA 2 82.72 84.6 6.07 5.61 4.58

TABLE 6 ICS-4 ICS-5 ICS-6 60°Gloss 85 >80 >80 Pendulum Hardness [sec] 24hr 40 >70 40 7 day 75 >120 60 Cross-Hatch Adhesion 4B-5B 2-3B 4B-5B MEKResistance [double rubs] 25% Film Loss >100 >100 >100 Water Resistance(24 hr) covered 4 4 4-5 Impact Resistance - Direct (in-lbs) 30 20 >100Mandrel Bend (0.5″) Pass Fail Pass

ICS-4, ICS-5, and ICS-6 results illustrate that all of these inventivecoatings have good MEK resistance which indicates that the coatings canbe cured at ambient temperature. Also, the coating performance dependson the T_(g) of polycarbamate materials. High T_(g) polycarbamateprovided harder but less flexible coating, while the lower T_(g)polycarbamate materials gave relatively softer but very flexiblecoatings. Therefore, these polycarbamates can be used alone in thecoating formulation, or by blending two or more than two polycarbamateswith different T_(g) to balance the coating properties to meet theapplication requirements.

Test Methods

Test methods include the following:

OH Number Titration

Where OH # is the magnitude of the hydroxyl number for a polyol asexpressed in terms of milligrams potassium hydroxide per gram or polyol(mg KOH/g polyol). Hydroxyl number (OH #) indicates the concentration ofhydroxyl moieties in a composition of polymers, particularly polyols.The hydroxyl number for a sample of polymers is determined byacetylation with pyridine and acetic anhydride in which the result isobtained as a difference between two titrations with potassium hydroxidesolution, one titration with a blank for reference and one titrationwith the sample. A hydroxyl number is the weight of potassium hydroxidein milligrams that will neutralize the acetic anhydride capable ofcombining by acetylation with one gram of a polyol. A higher hydroxylnumber indicates a higher concentration of hydroxyl moieties within acomposition. A description of how to determine a hydroxyl number for acomposition is well-known in the art, for example in Woods, G., The ICIPolyurethanes Book, 2^(nd) ed. (ICI Polyurethanes, Netherlands, 1990).Hydroxyl equivalent weight (OH EW) is calculated using the followingformula

OH EW=56100/OH #

Percent Solids (Polycarbamate or Polyol)

Approximately 0.5 g of polymer is weighed into an aluminum weighingdish. Approximately 1 ml of toluene is added to the aluminum weighingdish. Duplicate weighing dishes are prepared and placed in a 105° C.oven for greater than 4 hours. The percent solids are calculated usingthe following formula:

% Solids=100×(final sample weight/initial sample weight)

The percent solids are an average of the duplicate samples.

T_(g) Determination

The T_(g) (glass transition temperature) is measured using a DSC1000from TA Instruments. Between 7-14 mg of dried polymer (sample taken frompercent solids test) was weighed into a DSC pan. The pan was heated fromroom temperature to 150° C. at 10° C./min; then cooled to −100° C. at10° C./min and heated again to 150° C. at 10° C./min.

Rain Erosion

Rain erosion testing is a test for evaluating the erosion resistance ofcoatings on wind turbine blades. It simulates the effect from collisionswith rain, dust, etc by spraying water over the coated surface of fastmoving test specimens. A suitable apparatus for measuring the rainerosion of the coating is the Air Force Research Laboratory Materials &Manufacturing Rain Erosion Test Apparatus, described hereinbelow.

The composite leading edge airfoil specimen configuration is shown inFIG. 1 and described above. Configuration 2 was used for examples CCS-Aand ICS-1, 2 and 3 and the test was performed at 240 miles per hour(MPH) for up to 60 min.

Referring to FIG. 2, the rotating arm apparatus consists of an eightfoot diameter, double arm blade designed to produce high tip velocitieswith zero lift and low drag coefficient. Duplicate test specimens aremounted at the leading edge tip sections of the double rotating arm. Thespecimens can be rotated at variable velocities between 100 and 650 MPH.The double arm blade is mounted horizontally on a vertical drive shaft(see FIG. 2). The simulated rainfall is produced by four curbed manifoldquadrants. Each manifold has 24 equally-spaced capillaries. De-ionizedwater is delivered to the four manifold quadrants simultaneously from awater storage tank. Temperature controlled water then fills thecapillaries to produce raindrops. Drop size and drop rate are controlledby the water temperature, capillary orifice diameter, and head pressureof the water storage tank. Raindrops from the simulation apparatusimpact the test specimens throughout their entire annular path. Dropsize and drop rate are approximately 1.8 to 2.0 mm and 6 to 7 drops persecond, respectively. Calibration of the water supply system isscheduled on a regular basis. All functions of the apparatus arecontrolled and monitored from the remote control room. Instantaneousvelocity readout is monitored by an integrating digital voltmeter.Variable speed operation is possible through the operator's manualcontrol. Magnetic pickups and high intensity strobe lights provide stopmotion viewing of the test specimens under actual test conditions.Closed-circuit television cameras and monitors allow the operator tovisually observe the test specimens undergoing rain field exposure.Tests can also be videotaped for later study.

Observations were made via video during the testing noting when erosionoccurred through the topcoat to the primer or substrate (color change).A time>30 min is considered acceptable; more preferred is a time>45 min;and most preferred is a time of 60 min without any pitting to the primeror substrate. The acceptance criteria used was no visible damage to thetopcoat after the various testing times.

Gloss

Gloss is measured using a BYK micro-TRI-gloss instrument. Gloss is ameasure of light reflectance of a coating at defined angles. Gloss ismeasured at 60°.

Pendulum Hardness

Pendulum hardness testing is performed according to ASTM D4366 method,and average of 3 measurements are averaged and reported.

Cross-Hatch Adhesion

Cross-hatch adhesion was measured and rated according to ASTM D-3359.Specific ASTM ratings for the adhesion test are shown in Table below.Adhesion ratings of 4 B and 5 B are desired.

ASTM D-3359 Classification for Adhesion Rating Percent of CoatingRemoved 5B  0% (Perfect adhesion) 4B  <5% 3B  5-15% 2B 15-35% 1B 35-65%0B >65%

MEK Double Rubs

Solvent resistance and degree of crosslinking is evaluated by using asemi-automated MEK rub test machine (DJH Designs Inc.). The coatedsubstrates were rubbed with a cloth soaked in methyl ethyl ketone (MEK)that is attached to the rubbing block. Each back and forth rub counts asone double rub. This machine applies constant downward pressure (80psi), constant speed (70 double rubs/min) and counts the number ofdouble strokes applied.

Water Resistance

Water resistance was tested by exposing the coatings to DI water, withmethodology similar to ASTM D1308. A big DI water droplet was placed onthe coating surface and covered with a watch glass for 24 hrs. After 24hrs, the water was wiped off the coating. The coating was visuallyinspected for any signs of color change, staining, blistering, etc. Thecoating was rated as a 5 (no effect) through 1 (severe blistering orcompletely dissolved).

Impact Resistance

The impact resistance of the coating was determined by using a Gardnerimpact tester according to ASTM D2794.

Mandrel Bend test

The mandrel bend test is to evaluate the coating's resistance tocracking (flexibility). The coated panels are bent over a mandrel andthe resistance to cracking of the coating is determined. The results arerecorded if the coating pass or fail the mandrel with 0.5′ diameter.

The present invention may be embodied in other forms without departingfrom the spirit and the essential attributes thereof, and, accordingly,reference should be made to the appended claims, rather than to theforegoing specification, as indicating the scope of the invention.

We claim:
 1. A crosslinkable coating composition comprising: (a) apolyaldehyde, or acetal or hemiacetal thereof; (b) an acid catalysthaving pKa of less than 6; (c) a liquid media; (d) an acrylicpolycarbamate comprising at least an average of 2.0 carbamate functionalgroups, wherein said polycarbamate has a glass transition (Tg) of lessthan 25° C.; (−50 to less than 5); and (e) one or more fillers having apH in the range of equal to or less than 9 and/or one or more pigmentshaving a pH in the range of equal to or less than 9, and/or one or moreadditives having a pH in the range of equal to or less than 9, whereinsaid composition has a curing temperature in the range of less than 70°C.
 2. A process for producing a crosslinkable coating compositioncomprising the steps of: (a) selecting a polyaldehyde, or acetal orhemiacetal thereof; (b) selecting an acid catalyst having pKa of lessthan 6; (c) selecting a liquid media; (d) selecting a acrylicpolycarbamate comprising at least an average of 2.0 carbamate functionalgroups wherein said polycarbamate has a glass transition (Tg) of lessthan 25° C.; (−50 to less than 5); (e) selecting one or more fillershaving a pH in the range of equal to or less than 9, and/or one or morepigments having a pH in the range of equal to or less than 9, and/or oneor more additives having a pH in the range of equal to or less than 9;(f) contacting said polyaldehyde, or acetal or hemiacetal thereof; saidacid catalyst; said liquid media, said polycarbamate, said one or morefiller, and optionally said one or more pigments; and (g) therebyforming a crosslinkable coating composition; wherein said compositionhas a curing temperature in the range of less than 70° C.
 3. A coatedsubstrate comprising: a substrate; and one or more film layers derivedfrom the crosslinkable coating composition of claim 1 associated with atleast one surface of said substrate.
 4. A rotor blade comprising: ablade having at least one surface; one or more film layers derived fromthe crosslinkable coating composition of claim 1 associated with atleast one said surface of said blade.
 5. The rotor blade of claim 4,wherein said rotor blade is a wind turbine blade, a helicopter blade, oran aircraft blade.
 6. The coated substrate of claim 1, wherein saidsubstrate comprises one or more metals, one or more plastics, one ormore composite materials, and one or more films derived from one or moreprimers.
 7. The crosslinking coating composition of claim 1, whereinsaid polycarbamate has a glass transition (Tg) of less than 0° C.
 8. Thecoated article according to claim e, wherein said one or more filmlayers have a thickness in the range of from 5 to 500 μm.
 9. The coatedarticle of claim 3, wherein said one or more films have an MEKresistance in the range of from greater than 50 double rubs.
 10. Therotor blade of claim 4, wherein said one or more films have rain erosionresistance of greater than 30 minutes.
 11. The crosslinkable compositionof claim 1, wherein said polyaldehyde, acetal or hemiacetal thereof hasfrom 2 to 20 carbon atoms or from more than 20 carbon atoms, with theproviso that a polyaldehyde having more than 20 carbon atoms has atleast one aldehyde group for every 10 carbon atoms.
 12. Thecrosslinkable composition of claim 11, wherein said polyaldehyde, acetalor hemiacetal thereof is selected from the group consisting of(cis,trans)-1,4-cyclohexanedicarboxyaldehydes,(cis,trans)-1,3-cyclohexanedicarboxyaldehydes, and mixtures thereof. 13.The crosslinkable composition of claim 1, wherein the acrylicpolycarbamate component has carbamate groups and hydroxyl groups in aratio of the equivalents of carbamate groups to the number ofequivalents of hydroxyl functional groups of from 1:1 to 20:1.
 14. Thecrosslinkable composition of claim 1, where said crosslinkablecomposition further comprises one or more curing inhibitors.
 15. Thecrosslinkable composition of claim 1, wherein the curing inhibitor ischosen from water, an alcohol or a mixture thereof.